DTIC ADA320417: The Effects of Secondary Flows on the Convective Heat Transfer from a Heated Block in an Airstream

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4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
The Effects of Secondary Flows on the Convective Heat Transfer from a Heated Block
in an Airstream
6. AUTHOR(S)
Scott E. LeClaire
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
University of Maine REPORT NUMBER
96-132
9. SPONSORINGIMIONITORING AGENCY NAME(S) AND AOORESS(ES) 10. SPONSORINGIMIONITORING
DEPARTMENT OF THE AIR FORCE AGENCY REPORT NUMBER
AFIT/CIA
2950 P STREET
WPAFB OH 45433-7765
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The Effects of Secondary Flows
on the Convective Heat Transfer from a
Heated Block in an Airstream
by
Scott E. LeClair
A THESIS
Submitted in Partial Fulfillment of the
Requirements for the Degree of
Master of Science
(in Mechanical Engineering)
The Graduate School
University of Maine
May, 1996
Advisory Committee:
Michael T. Boyle, Associate Professor of Mechanical Engineering, Thesis Advisor
William C. Rivard, Professor of Mechanical Engineering
Justin H. Poland, Associate Professor of Mechanical Engineering
James Sucec, Professor of Mechanical Engineering
czJ- TYT T ,
The Effects of Secondary Flows
on the Convective Heat Transfer from a
Heated Block in an Airstream
by Scott E. LeClair
An Abstract of the Thesis Presented in Partial
Fulfillment of the Requirements of the Degree of
Master of Science ( in Mechanical Engineering)
May, 1996
A detailed investigation into the secondary flow effects on the convective heat
transfer from a heated, low-profile, block in an airstream is presented. The block
surfaces are heated by driving a direct current though stainless steel strips, adhered in a
series circuit configuration on the block's surfaces. Measurements of the temperature
distributions, on the front, top, rear, and lateral block surfaces, are taken via an
automated data acquisition system equipped with 79 resistive type temperature sensors.
The temperature sensors are installed between the stainless steel strips and the block
substrate material. From the temperature measurements, local surface coefficient of
heat transfer values are reduced, by performing an energy balance on a small region of
stainless steel in the vicinity of each sensor. An overall, three-dimensional, convection
heat transfer description for the block, at a Reynold's number (based on the block
height) of approximately 21000 is presented. Also investigated are the heat transfer
effects produced by varying freestream flow Reynold's number and average Grashof
number. Further elaborating the flow field conditions present on the block's cover
surface, flow visualization studies, using a modified ink-dot and oil of wintergreen
method, are conducted. These studies are performed at freestream flow Reynold's
numbers of 15000, 22000, 33000, and 51000.
Acknowledgments:
The author gratefully acknowledges the contributions of the University of Maine's
Department of Mechanical Engineering community, without whom this work would not
have been possible. K. A. Asante provided his skill in the construction of the heated
block and board assembly. James Van Sandt and Peter Guyette provided their efforts
and guidance in the creation and support of the computer data acquisition systems.
Arthur Pete and Steve Webber facilitated the experimental equipment installations and
the maintenance of the wind tunnel laboratory. Sincerest thanks are expressed to
associate professor Michael Boyle for initiating the project, and providing enduring
guidance and direction throughout the entire thesis process.
Lastly, the author would like to dedicate this work to his wife, Dina, and son,
Alden. Their unconditional support and encouragement provided the drive required to
pursue and accomplish this work.
Table of Contents:
Acknowledgem ents .................................................................................. ii
I. List of Tables ....................................................................................... v
II. List of Figures ..................................................................................... vii
II1. Nom enclature .......................................................................................... x
IV. Introduction .......................................................................................... 1
V. Background .......................................................................................... 3
VI. Experimental Apparatus and Set-up
A. Experimental Block and Board Assembly ............................... 12
B. Heat Transfer Data Monitoring and Recording Systems ......... 17
C. Flow Visualization Study Procedures ..................................... 23
D. W ind Tunnel Test Facility ...................................................... 25
VII. Testing Conditions ............................................................................ 28
VIII. Data Reduction Schem e ................................................................... 30
IX. Uncertainty ........................................................................................ 36
X. Results
A. Block Cover Flow Visualization Testing .................................. 39
B. Three-Dimensional Heat Transfer Description ........................ 47
C. Effect of Reynold's Num ber .................................................... 60
D. Effect of Gr ashof Num ber ....................................................... 71
XI. Conclusions ....................................................................................... 87
XII. References ....................................................................................... 94
XII. Appendices
A. Mi scellaneous Tables and Figures ......................................... 96
B. RTD Calibration Procedure and Data ....................................... 100
iii
C. Detailed Uncertainty Analysis ................................................... 111
D. Data Acquisition and Calibration Software ................................ 118
E. Equipm ent Listing ..................................................................... 140
F. Testing Data Tables and Figures ............................................. 141
G . Flow Visualization Test M odification ......................................... 300
XIV. Biography of the Author ....................................................................... 304
iv
I. List of Tables:
Table 1: Experimental Testing Conditions ....................................................... 29
Table 2: Test Data Uncertainty ........................................................................ 38
Table 3: Specific Average Uncertainties .......................................................... 38
Table A-1: Property Analysis Table ...................................................................... 99
Table B-1: Hotbox Low Temperature Calibration Data .......................................... 103
Table B-2: Low Temperature Sensor Calibration Equations and Performance ...... 105
Table B-3: Hotbox High Temperature Calibration Data ......................................... 107
Table B-4: High Temperature Sensor Calibration Equations and Performance ..... 109
Table C-1: Uncertainty Analysis Summary ............................................................ 116
Table F-1: Example Test Data Log ....................................................................... 142
Table F-2 Testing Data Tables
to F-7: Test 10-25_1 ........................................................................................ 143
Table F-8 Testing Data Tables
to F-13: Test 10-30_1 ........................................................................................ 154
Table F-14 Testing Data Tables
to F-19: Test 11-01_1 a ...................................................................................... 164
Table F-20 Testing Data Tables
to F-25: Test 11-02_1 ........................................................................................ 174
Table F-26 Testing Data Tables
to F-31: Test 11-13_1 ......................................................................................... 184
Table F-32 Testing Data Tables
to F-37: Test 11-14_1 ........................................................................................ 194
Table F-38 Testing Data Tables
to F-43: Test 11-15_1 ........................................................................................ 204
Table F-44 Testing Data Tables
to F-49: Test 11-21_1 ........................................................................................ 214
Table F-50 Testing Data Tables
to F-54: Test 12-11_1 ........................................................................................ 224
V
Table F-55 Testing Data Tables
to F-59: Test 12-12_1 ........................................................................................ 233
Table F-60 Testing Data Tables
to F-64: Test 12-14_1 ........................................................................................ 242
Table F-65 Testing Data Tables
to F-69: Test 12-14 2 ........................................................................................ 251
Table F-70 Testing Data Tables
to F-75: Test 01-31_1 ........................................................................................ 260
Table F-76 Testing Data Tables
to F-81: Test 02-01_1 ........................................................................................ 270
Table F-82 Testing Data Tables
to F-87: Test 02-21_1 ........................................................................................ 280
Table F-88 Testing Data Tables
to F-93: Test 02-27_1 ........................................................................................ 290
vi
II. List of Figures:
Figure 1: Two-Dimensional Blunt Plate Set-up .................................................... 3
Figure 2: Three-Dimensional Qualitative Flow Description ................................ 11
Figure 3: Block and Board Assembly - Top View ............................................. 12
Figure 4: Block and Board Assembly - Side View ............................................. 12
Figure 5: Block and Board Assembly - Front View ........................................... 13
Figure 6: RTD Mounting Detail .......................................................................... 15
Figure 7: Monitoring and Recording System Detail ........................................... 17
Figure 8: Model Orientation Detail .................................................................... 19
Figure 9: W ind Tunnel Detail ............................................................................ 25
Figure 10: Wind Tunnel Test Section Detail ...................................................... 26
Figure 11: Temperature Sensor Control Volume Detail ....................................... 30
Figure 12: Block Cover Flow Visualization
NRe = 15030, Freestream Velocity = 455 FPM .................................. 40
Figure 13: Block Cover Flow Visualization
NRe = 21802, Freestream Velocity = 660 FPM .................................. 41
Figure 14: Block Cover Flow Visualization
NRe = 33034, Freestream Velocity = 1000 FPM ................................. 42
Figure 15: Block Cover Flow Visualization
NRe = 51202, Freestream Velocity = 1550 FPM ................................. 43
Figure 16: Reattachment Length vs. Reynold's Number (Cover Surface) ........... 45
Figure 17: Coordinate System Detail ................................................................. 47
Figure 18: 3-D Composite Temperature Difference Surface Plot
Tests 11-13, 14 (Cover Surface) ...................................................... 48
Figure 19: 3-D Composite Nusselt Number Surface Plot
Tests 11-13, 14 (Cover Surface) ...................................................... 49
Figure 20: Tests 11-13, 14: Composite Nusselt Number Contour Chart
(C over Surface) ................................................................................ 50
Figure 21: Test 01-31_1: Nusselt Number Contour Chart (Front Surface) ....... 51
vii
Figure 22: Test 11-13_1: Nusselt Number Contour Chart (Left Lateral Surface) ..... 52
Figure 23: Test 02-01_1: Nusselt Number Contour Chart (Rear Surface) ........... 53
Figure 24: 3-D Composite Nusselt Number Surface Plot
Tests 11-01, 02 (Cover Surface) ........................................................ 61
Figure 25: Tests 11-01, 02: Nusselt Number Contour Chart (Cover Surface) ......... 62
Figure 26 Test 11-02_1: Nusselt Number Contour Chart (Left Lateral Surface) ..... 63
Figure 27: Test 10-30_1: Nusselt Number Contour Chart (Front Surface) ....... 64
Figure 28: 3-D Composite Nusselt Number Surface Plot
Tests 11-15, 21 (Cover Surface) ........................................................ 65
Figure 29: Tests 11-15, 21: Nusselt Number Contour Chart (Cover Surface) ......... 66
Figure 30: Test 11-21_1: Nusselt Number Contour Chart (Left Lateral Surface) ..... 67
Figure 31: Standard Deviation in Nusselt Number vs. Reynold's Number ........... 68
Figure 32: Average Nusselt Number vs. Reynold's Number
(Grashof Number Fixed at Approximately 3x1 07) ................................ 69
Figure 33: 3-D Composite Temperature Difference Surface Plot
Tests 12-11, 02-21 (Cover Surface) .................................................. 72
Figure 34: 3-D Composite Nusselt Number Surface Plot
Tests 12-11, 02-21 (Cover Surface) .................................................. 73
Figure 35: Tests 12-11, 02-21: Nusselt Number Chart
(C over Surface) ................................................................................ 74
Figure 36: Test 02-21: Nusselt Number Chart
(Left Lateral Surface) ........................................................................ 75
Figure 37: 3-D Composite Temperature Difference Surface Plot
Tests 12-12, 02-27 (Cover Surface) .................................................. 76
Figure 38: 3-D Composite Nusselt Number Surface Plot
Tests 12-12, 02-27 (Cover Surface) .................................................. 77
Figure 39: Tests 12-12, 02-27: Nusselt Number Contour Chart
(Cover Surface) ................................................................................ 78
Figure 40: Test 02-27: Nusselt Number Contour Chart
(Left Lateral Surface) ........................................................................ 79
viii